Can anyone tell me the answers to questions 20 on page 75 and 21 on page 76 of the Physics 8 class a

Molecular Physics Molecular physics is the study of the structure of molecules, the physical properties of molecules, and the interactions between molecules; It is a branch of physics that studies the physical properties of gases, liquids, and solids, especially those related to thermal phenomena. Molecular physics is closely related to other branches of physics such as atomic physics, condensed matter physics, physical mechanics, as well as physical chemistry, chemical kinetics, quantum chemistry, etc. Molecular structure involves not only the equilibrium geometric configuration of the atoms (nucleus, to be exact) that compose it, but more importantly, the interaction of the various components of the molecule – chemical bonding.

The physical properties of a molecule are related to the chemical structure of the molecule, so studying the properties of a molecule can determine its chemical structure. Quantum mechanics is the basic theory that studies the nature of chemical bonds, the physical properties of molecules, and the interactions between molecules. Since 1930, quantum mechanics has made great progress in the theoretical explanation of these problems.

Quantum mechanics of molecules, quantum chemistry, is one of the active frontiers of near-the-world chemistry. Remarkable achievements have been made in applying the principles of quantum chemistry and using electronic computer technology to directly calculate the energy level, state wave function and other physical properties of molecules. Molecular physics studies the physical properties of molecules from many aspects.

It studies the relative vibration of atoms in molecules, the rotation of molecules, the movement of electrons in molecules, and the phenomena generated by intermolecular forces. Molecular spectroscopy is an important means to study molecular structure, which provides a lot of knowledge about molecular structure and molecular dynamics, and the correspondence between these spectra and their quantum mechanical explanations is an important basis for confirming quantum theory in history. Techniques such as radio frequency and microwave spectroscopy, atomic and molecular beams, and laser spectroscopy enable highly accurate measurements of the fine and ultrafine structure of these spectra, allowing the determination of nuclear spin, nuclear four-plate moments, and nuclear mass.

The study of the physical properties of molecules also includes the study of the electromagnetic properties of molecules (the behavior of molecules in electric and magnetic fields), that is, the polarizability and magnetic susceptibility of molecules, as well as the thermal properties of molecules. X-ray diffraction, neutron diffraction and other techniques can be used to directly determine the structure of molecules. The photoelectron spectroscopy that has been developed is also a powerful experimental method for studying the physical properties of molecules.

Molecular physics starts from the study of the molecular structure of matter and the interaction of molecular problems, and studies the thermal properties and aggregation state of matter, including the equation of state (the relationship between volume, temperature and pressure), various thermodynamic functions, surface layer phenomena of liquids and solids, surface adsorption, coherence equilibrium and phase transition, and transport phenomena such as diffusion, heat conduction and viscosity, etc. Since these phenomena and properties are related to the overall state of motion of a large number of molecules, the laws of thermodynamics and the theories of statistical physics are also widely used in molecular physics.

You don't write the question, how can I help you solve it.

Solution: 1) The buoyancy f float = g row = mg = 1000 1000kg 10n kg = 107n

Answer: The buoyancy experienced by the ship is 107N

The volume of the discharged river water v row = f float g = 107n1000kg m3 10n kg = 1000m3

A: The volume of drained river water is 1000m3

3).Because the density of the wooden block is less than the density of the water, the wooden block floats without levitation, because the wooden block floats, so g = f floats, so p wood v wood g = p water v row g is 800 * 200 = 1000 * v row.

V row = 160 cubic centimeters.

That is, the volume immersed in water is 160 cubic centimeters.

4) Solid volume v=120cm3=

The maximum buoyancy that a solid can be subjected to by a salt water is .

f=pvg=(

Because of f, it sinks.

The bottom of the container supports it for:

f'=g-f=

Is it a human-taught version or a version of this, I need to know what the problem is.

Solution: 1) The buoyancy f float = g row = mg = 1000 1000kg 10n kg = 107n

Answer: The buoyancy experienced by the ship is 107N

The volume of the discharged river water v row = f float g = 107n1000kg m3 10n kg = 1000m3

A: The volume of drained river water is 1000m3

3).Because the density of the wooden block is less than that of water, the wooden block floats without being suspended.

Because the wooden block floats, g = f floats, so p wood v wood g = p water v row g is 800 * 200 = 1000 * v row.

V row = 160 cubic imitation guess silver feast centimeters.

That is, the volume immersed in water is 160 cubic centimeters.

4) Solid volume v=120cm3=

The maximum buoyancy that a solid can be subjected to by a salt water is .

f=pvg=(

Because of f, it sinks.

The bottom of the container supports it for:

f'=g-f=

The main content of the answer in physics for science enthusiasts is (1) f floats < g and sinks; (2) F float > g, float (3) F float = g, suspend or float.

Method 2: (Compare the density of the object to the liquid).

1) f float < g, sinking; (2) f float > g, float (3) f float = g, levitate. (does not float).

3 The cause of buoyancy is that an object immersed in a liquid is subjected to the difference between the upward and downward pressure of the liquid on it.

4 Archimedes' principle: An object immersed in a liquid experiences an upward buoyant force equal to the gravitational force expelled by the liquid it displaces. (The buoyancy force exerted on an object immersed in gas is equal to the gravitational force it expels from the gas).

5 Archimedes' Principle Formula:

6 The methods for calculating buoyancy are:

1) Weighing method: f float = g — f, (g is the object subjected to gravity, f is the reading of the spring scale when the object is immersed in liquid).

2) Pressure difference method: f float = f up - f down.

3) Archimedes' principle:

4) Equilibrium method: F float = g matter (suitable for floating, suspension).

7 Buoyancy utilization.

2) Submarine: Sink and float by changing its own gravity.

3) Balloons and airships: filled with gases that are less dense than air.

The speed is at least: sv1 root number (s2+l2).

The direction is the bow obliquely upstream, and the angle between the bow and the water velocity is: arccos [S root number under (S2+L2)].

The oblique countercurrent direction is 45 degrees, and the size is 2sv1 (L. root number 2).

Let the eight unknowns be a, b, c, d, e, f, g, h, a+b=c+d=e+f=g+h

and a=b=c=d

So b=d=e=f